The capture of a high-quality image associated with a moving subject in a low-light situation is necessary for security and surveillance applications such as, for example, biometric acquisition. Biometric acquisition and surveillance require good illumination of the subject to acquire a high quality image for biometric processing. Many other constraints such as, for example, subject motion tolerance and depth of focus, may be relaxed if the level of illumination is increased.
Imaging systems employed in security and surveillance may be designed to generate accurate images of subjects utilizing a camera and a near infrared (IR) illumination so that they are inconspicuous and able to work in darkness. In addition, some applications, such as iris biometrics, are designed to acquire images illuminated with near infrared (IR) illumination. In some instances, infrared illumination may cause damage to, or otherwise alter, the object being imaged. One such object that can be damaged by excessive illumination is the human eye. In the majority of prior art imaging systems, the intensity of light from the infrared illumination projected onto the subject does not vary as the distance between the camera lens and the subject is varied. Hence, the amount of power that a flash may require to sufficiently illuminate a specific subject at a distance may easily exceed eye safety limits if the subject is positioned at a close range. The fundamental problem is to get as much illumination as possible on a subject at longer ranges while maintaining eye safe levels at close ranges.
Based on the foregoing, it is believed that a need exists for an improved distributed agile illumination system and method for projecting a large amount of illumination on a specific subject at a long distance and at an eye safe level of illumination and additionally at a close range, as described in greater detail herein.